diff options
| -rw-r--r-- | cryptography/hazmat/primitives/hmac.py | 11 | ||||
| -rw-r--r-- | docs/hazmat/primitives/hmac.rst | 14 | ||||
| -rw-r--r-- | tests/hazmat/primitives/test_hmac.py | 14 |
3 files changed, 36 insertions, 3 deletions
diff --git a/cryptography/hazmat/primitives/hmac.py b/cryptography/hazmat/primitives/hmac.py index 1a67b332..1bbe39c7 100644 --- a/cryptography/hazmat/primitives/hmac.py +++ b/cryptography/hazmat/primitives/hmac.py @@ -15,6 +15,7 @@ from __future__ import absolute_import, division, print_function import six +from cryptography.exceptions import AlreadyFinalized from cryptography.hazmat.primitives import interfaces @@ -37,11 +38,15 @@ class HMAC(object): self._ctx = ctx def update(self, msg): + if self._ctx is None: + raise AlreadyFinalized("Context was already finalized") if isinstance(msg, six.text_type): raise TypeError("Unicode-objects must be encoded before hashing") self._ctx.update(msg) def copy(self): + if self._ctx is None: + raise AlreadyFinalized("Context was already finalized") return HMAC( self._key, self.algorithm, @@ -50,4 +55,8 @@ class HMAC(object): ) def finalize(self): - return self._ctx.finalize() + if self._ctx is None: + raise AlreadyFinalized("Context was already finalized") + digest = self._ctx.finalize() + self._ctx = None + return digest diff --git a/docs/hazmat/primitives/hmac.rst b/docs/hazmat/primitives/hmac.rst index bd1a4934..cff2dbf1 100644 --- a/docs/hazmat/primitives/hmac.rst +++ b/docs/hazmat/primitives/hmac.rst @@ -36,15 +36,25 @@ message. .. method:: update(msg) :param bytes msg: The bytes to hash and authenticate. + :raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize` .. method:: copy() - :return: a new instance of this object with a copied internal state. + Copy this :class:`HMAC` instance, usually so that we may call + :meth:`finalize` and get an intermediate digest value while we continue + to call :meth:`update` on the original. + + :return: A new instance of :class:`HMAC` which can be updated + and finalized independently of the original instance. + :raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize` .. method:: finalize() Finalize the current context and return the message digest as bytes. - Once ``finalize`` is called this object can no longer be used. + Once ``finalize`` is called this object can no longer be used and + :meth:`update`, :meth:`copy`, and :meth:`finalize` will raise + :class:`~cryptography.exceptions.AlreadyFinalized`. :return bytes: The message digest as bytes. + :raises cryptography.exceptions.AlreadyFinalized: diff --git a/tests/hazmat/primitives/test_hmac.py b/tests/hazmat/primitives/test_hmac.py index 4186967a..d17049e3 100644 --- a/tests/hazmat/primitives/test_hmac.py +++ b/tests/hazmat/primitives/test_hmac.py @@ -19,6 +19,7 @@ import pytest import six +from cryptography.exceptions import AlreadyFinalized from cryptography.hazmat.primitives import hashes, hmac from .utils import generate_base_hmac_test @@ -49,3 +50,16 @@ class TestHMAC(object): def test_hmac_algorithm_instance(self): with pytest.raises(TypeError): hmac.HMAC(b"key", hashes.SHA1) + + def test_raises_after_finalize(self): + h = hmac.HMAC(b"key", hashes.SHA1()) + h.finalize() + + with pytest.raises(AlreadyFinalized): + h.update(b"foo") + + with pytest.raises(AlreadyFinalized): + h.copy() + + with pytest.raises(AlreadyFinalized): + h.finalize() |